The world should brace itself for an increase in infectious diseases like SARS because of a fatal under-estimation of the power of viruses and bacteria, an expert said today.

Professor Peter Curson, a historical epidemiologist at Sydney's Macquarie University, said Severe Acute Respiratory Syndrome was in many ways a monster of man's own making, along with other new diseases like AIDS and Ebola.

He said human behaviour had created a situation where basically benign infections existing in the environment or among animals and humans had been given a "leg-up".

Prof Curson said the world was now entering a phase of public health where infective agents were becoming more aggressive and where a whole new range of disease was emerging.

However the medical community had got it wrong by writing off infectious diseases after the eradication of smallpox in 1979 and focusing on lifestyle, chronic and degenerative conditions, like cancer and obesity. ");document.write("

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"That reflects that we've undervalued the biophysical environment, we've sort of regarded it as a stationary target," Prof Curson said.

Instead of a magic bullet, antibiotics had created resistant infections, he said.

Meanwhile, humans tampered with the environment to the extent that the effects were now being seen in the form of mutated viruses.

"I believe that the next ten to 15 years will see a substantial increase in infectious disease," Prof Curson said.

"I'm sure we're going to see a lot more interesting exotic infections."

He said in the past Australia was protected from infectious diseases by its geography, but this was no longer the case.

Originally, Australia relied on infections "burning out" during the long trip back or being contained by lengthy quarantine requirements.

But air travel and an appetite to travel to more exotic destinations had changed things.

Prof Curson said the rise of infectious diseases should be a lesson in human hubris.

"There is a bit of an arrogance, in a sense we are just one of a competing series of species and bacteria, and viruses are probably more significant in the whole scheme of things than we are," he said.